4.6.1 Forces

Question 1

What is the difference between scalar and vector quantities?

Answer 1

scalar quantities just have a magnitude (a number)

Vector quantities have a magnitude and a direction

i.e. 10 miles is a scalar quantity

10 miles North would be vector

Question 2

Is Force a scalar or vector quantity?

Answer 2

Vector - as forces act in a certain direction

Question 3

How can we represent a vector with a diagram?

Answer 3

Use an arrow. The size of the arrow shows the magnitude - the direction shows the direction!

Question 4

What is the difference between a contact and non contact force?

Answer 4

In contact forces the objects must be physically touching i.e. friction between the road and a tyre.

Non contact forces the objects can be physically separated i.e. a magnet is attracted to another magnet even though it is not touching.

Question 5

Give some examples of contact forces.

Answer 5

Friction, air resistance, tension, normal contact force (upthrust)

Question 6

Give some examples of non contact forces

Answer 6

magnetism, gravity, electrostatic forces

Question 7

What is the equation for work done?

What unit does each part need to be in?

Answer 7

Work done = distance x force

Work done in Joules (J)
Distance in metres (m)
Force in Newtons (N)

Question 8

What is the definition of a ‘joule’ of energy.

Answer 8

A joule is 1 newton metre. This is because one joule of energy is used when a force of 1N moves an object by 1 metre.

Question 9

What is the difference between weight and mass?

Answer 9

Mass depends on how many atoms something is made of.

Weight is the force acting on an object due to gravity.

Question 10

What is the equation to find weight?

Answer 10

Weight (N) = Mass (kg) x gravitational field strength (N/kg)

Question 11

What is the relationship between mass and weight?

Answer 11

It is directly proportional. If mass doubles, then so does weight.

Question 12

Would your mass be different on the moon?

Would your weight be different on the moon?

Explain your answer.

Answer 12

Your mass would be the same as the amount of atoms you are made up of does not change.

Your weight would change. It would be less on the moon as the gravitational field strength is weaker.

Question 13

How can we measure weight?

Answer 13

Using a newton meter. This measures weight in Newtons.

Question 14

How can an object gain gravitational potential energy?

Answer 14

Raise it up above the ground. The higher your raise it the more potential it has.

Question 15

What is the equation to calculate gravitational potential energy?

Answer 15

GPE (J) = mass (kg) x gravitational field strength (N/kg) x height raised (m)

Question 16

What does it mean if an object has been ‘elastically deformed’?

Answer 16

If you stretch an object, like an elastic band, and it returns to its original shape it has been elastically deformed.

Question 17

What does it mean if an object has been ‘inelastically deformed’?

Answer 17

If you stretch an object, like plastercine, and it does not return to its original shape it has been inelastically deformed.

Question 18

What happens when you apply a force to a spring?

Answer 18

It stretches. The relationship between the force (weight) and the extension of the spring (how stretched it is) is directly proportional. As the force doubles the extension of the spring also doubles.

Question 19

What is the equation linked force and extension?

Answer 19

Force (N) = spring constant (N/m) x extension (m)

Question 20

How do you convert from cm to m?

How many metres are in 200cm?

Answer 20

divide by 100

2m

Question 21

How do you convert from km to m?

How many metres are in 0.5km?

Answer 21

multiple by 1000

500m

Question 22

What is the ‘limit of proportionality’?

Answer 22

This is the maximum amount of force that a spring/elastic band can take and stretch in an elastic way. Past the limit of proportionality there will not be a link between the force applied to the spring and the extension.

Question 23

What type of energy is stored in a compressed spring or a stretched elastic band?

Answer 23

Elastic potential energy

Question 24

What is the equation to calculate elastic potential energy?

Answer 24

elastic potential energy (J) = 0.5 x spring constant (N/m) x extension(m)squared

Question 25

Why do we need a spring constant in calculations?

Answer 25

All springs are different and need a different amount of force to stretch them.